Hello Lightning UK,
I think you should make "Include System Files" and "Include Hidden Files" checked in default setting. Yesterday I installed Imgburn 2.3.2.0 on a new computer, then added about 4 GB of files in build mode (user profiles, lots of hidden files), but the calculator kept sayin - 1,5 GB. Well, weird behavior as Total Commander indicated 4,2 GB. I didn't have enough time to investigate and thought it was some issue with the calculator, so I burnt the project. However, after that I examined freshly burnt disc with TC and found you know what - 1,5 GB of files. :-)
Then I looked more carefully into Imgburn settings and spotted those System and Hidden files options and checked them immediately and burnt the disc again correctly.
I know it was my fault. But if it is not a problem to check these two settings in default, many future users would be grateful. When I want to burn a directory - I want to burn everything, right? No matter if it is hidden or system.
Regards
Jack